Novel process for electrodepositing zinc

ABSTRACT

There is disclosed a process for electrodepositing zinc involving the use, as brightening additives, of complex mixtures containing salts of di-(1-benzyl-3-carboxyl-1,2-dihydropyridyl-2) ether and the salts of the corresponding sulfides and polysulfides. The use of the latter additives leads to the preparation of zinc coatings characterized by their excellent smoothness, brightness, luster and adherance.

United States Patent Aug. 28, 1973 Cope, Jr.

[54] NOVEL PROCESS FOR 3,296,105 1/1967 Rushmore 204/55 Y 3,318,787 5/1967 Rindt et al. ELECTRODEPOSITING ZINC 3,411,996 11/1968 Rushmere 204/50 Y [75] Inventor: Richard P. Cope, Jr., New City, NY. [73] Assignee: Stauffer Chemical Company, New Primary Examiner-R Edmundson 1 Y k Y AttorneyRobert C. Sullivan, Paul J. Juettner and Daniel S. Ortiz [22] Filed: Oct. 27, 1971 [21] Appl. No.: 193,203 [57] ABSTRACT There is disclosed a process for electrodepositing zinc [52] us. Cl. 204/55 Y, 204/DIG. 2 involving t u as ght n g additives, of pl x [51] Int. Cl C23b 5/10 mixtures containing salts of y xyl- [58] Field of Search... 204/55 Y, DIG. 2, 1,2-dihydropyridyl-2.) ether ndth l s of the corre- 204/52 Y, 54 L, 55 R sponding sulfides and polysulfides. The use of the latter additives leads to the preparation of zinc coatings char- [56] References Cit d acterized by their excellent smoothness, brightness, lus- UNITEDSTATES PATENTS 4/1956 Hoffman.. 204/55 Y ter and adherance. I

14 Claims, No Drawings l NOVEL PROCESS FOR ELECTRODEPOSITING ZINC RELATED APPLICATION Nicotinic acid, and various derivatives thereof, have long been known in the art. While nicotinic acid itself found early use as a food supplement, certain of its derivatives were found to be useful as electroplating brightening additives. For example, the inner salts of l-benzylpyridinium 3-carboxylate and p-xylylene, bis- (1-pyridinium-3-carboxylate) are disclosed for this use in U.S. Pat. No. 3,41 1,996, issued on Nov. 19, 1968, to J. D. Rushmere and N-allyl alkyl carboxylate pyridinium halides, N-benzyl alkylcarboxylate pyridinium halides and N-sulfoalkyl alkyl carboxylate pyridinium halides inter alia are disclosed in U. S. Pat. No. 3,318,787, issued on May 9, 1967 to Gustav'Rin'dt etal Other compounds related to nicotinic acid are disclosed in British Pat. No. 1,170,058 (complete specification published Nov. 12, 1969). i

Thus, the electrodeposition of zinc from alkaline cyanide zinc solutions is a widely utilized procedure for the preparation of coatings designed to protect ferrous metals by the means of a sacrificial cathodic reaction.

'The plating baths utilized in this process often contain one or more additives whose purpose is to provide the which are exceedingly smooth, bright, adherent and lustrous. Various other objects and advantages of this invention will be apparent from a reading of the disclosure which follows hereinafter.

TECHNICAL DISCLOSURE OF THE INYENTION It has now been discovered that zinc coatings characterized by their unusually high degree of smoothness,

, luster, adherence and brightness are obtainable from cyanide zinc plating baths which contain, as an addi tive, complex mixtures of a variety of water soluble compounds which include structures (A), (B), (C) and (D) corresponding to the formulae:

wherein Y" in (A), (B) and (C) is selected from the group consisting of oxygen and (S)x but wherein in (D) Y can only be (S)x;' M is a cation selected from the group consisting of hydrogen, sodium, potassium, lithium, zinc and ammonium; R and R are essentially hydrocarbyl groups containing from one to six carbon atoms inclusive and can be the same or different.

Z can be a halogen, carbalkoxy, carboxy, hydroxy or lower alkyl carboxylate group which can be the same or different, 1: is an integer having a value of from-1 'to 4 inclusive and can have a mixture of values of from 1 to 4; and a, c, and n are integers having a value of from zero to 2 inclusive and can be the same or different. It is, of course, understood that when a, c, or n have a value of zero, the substituent R R, or R, is not present and a hydrogen atom is present in its stead. In derivatives having the structure (A), (B) and (C)-the Y group is substituted upon either the two, four or six positions of a dihydropyridine ring. However, the precise points of attachment of the Y groups to the dihydropyridine ring in the compounds which comprise these complex mixtures is not readily ascertainable by the use of presently available analytical techniques and it seems likely that most or all of these three position isomers are present. Analytical data also indicate the presence of the pyridinium sulfide salt, especially at'pl-l values below 9.

The presence of other N-benzyl nicotinic acid derivatives including dipyridine 4,4; 2(6),4; or 2(6),2(6)

. compounds is also indicated. Thus, at least 20 different brightness.

compounds can be present in the complex mixtures used as additives in the plating process of this invention. 1

Thus, it has been found that the use of complex mixture containing water soluble species of the above .de-

scribed class of compounds in cyanide zinc plating baths yields zinc coatings characterized by their unusually high degree of smoothness, luster,adheren ce and As usedin this disclosure, the term essentially hydrocarbyl" is intended to include groups consisting essentially of carbon and hydrogen. It is of course understood that such groups can contain other groups which are relatively inert and do not change the basic nature of the substituent. Alkoxy, aryloxy, arylalkoxy, alkyloxyaryl, aryloxy, alkyl and alkoxyalkyl groups and polyalkyleneglycol residues are exemplary of such groups. When multiple ether groups are present, it is desired that no more than six be present in a substituent and,

of course, each substituent should contain no more than 12 carbon atoms inclusive.

Included within the definition of the term essentially hydrocarbyl are the aliphatic, cycloaliphatic and aromatic hydrocarbon moieties containing from about one to about six carbon atoms inclusive. Illustrative of the aliphatic hycarbon moieties are the alkyl moieties such as methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, propoxy, hexoxy, hexoxy, methoxymethyl, ethoxymethyl and ethoxyethyl groups and the like.

Illustrative of the cycloaliphatic hydrocarbon moieties are cycloalkyl groups such as cyclopentyl, cyclohexyl, cyclopentoxy, cyclohexoxy and the like. Illustrative of the aromatic hydrocarbon moieties are phenyl and phenoxy groups and the like.

For purposes of this invention, applicable halogen substituents are intended to include those having an atomic weight of less than 80 such as fluorine, chlorine and bromine. When the substituent Z is present as a halogen, it is preferred that the halogen be chlorine since this element is more readily commercially available than the other halogens and causes relatively little difficulty in respect to corrosion and handling.

As indicated above, Z can also represent inter alia, a lower alkylcarboxylate group. When Z represents'such a substituent, it is preferred that the lower alkyl group of the carboxylic acid ester contain from one to six car bon atoms and preferably from one to four carbon atoms. This preference is dictated both by economic factors and by the solubility characteristics of these compounds in the media where they will be used.

M in Formulae (A), (B), (C) and (D) hereinabove represents a cation selected from hydrogen, sodium, potassium, lithium, zinc and ammonium. Ammonium cations are of course well known. Intended to be included within this category are ammonium (NIL) and alkyl ammonium cations such as ethyl ammonium, trimethyl ammonium and the like. These ammonium ions can be represented by the formula:

wherein R R, are hydrogen and alkyl wherein the alkyl groups may each contain from one to three carbon atoms inclusive.

The preparation of the novel complex mixtures applicable for use in the plating process of this invention is quite simple and involves, in the case of the ether salts of structure (A), (B) and (C), and especially (B), the reaction between a pyridine salt, particularly l-benzyl-3-carboxy-pyridinium chloride, and an alkali metal or ammonium hydroxide with sodium hydroxide being preferred for this purpose. In conducting this reaction, the pyridinium salt is first dissolved in water which is heated to a temperature of from about to about 100 C. with the preferred range being from about 25 to C. This solution is then cooled down to a temperature of about 25 C. whereupon the alkali metal or ammonium hydroxide, which is first dissolved in water, is introduced. The reaction is allowed to proceed under agitation, at room temperature until its completion which is indicated by a change in the color of the solution from colorless to orangered. This ordinarily requires a reaction period of about one hour. While superatmospheric pressures can be employed in this reaction, it is preferred to employ atmospheric pressure. As thus prepared, the resulting complex mixture of compounds can be used as a plating bath additive in the form of the solution in which is it dissolved. Or, if desired, the solid reaction product may be obtained upon evaporation or distillation of the solution and then extracting this residue with a lower alkanol such as methanol.

The corresponding complex mixtures of sulfide and polysulfide salts of structure (A), (B), (C) and (D) as well as many other compounds present in these complex mixtures are prepared by means of a reaction which is essentially identical to the above described procedure used for preparing the mixtures of ether salts with the exception that an alkali metal, or ammonium, sulfide or polysulfide rather than an alkali metal, or ammonium, hydroxide is reacted with the l-benzyl-3- carboxy-pyridinium chloride salt. The preferred alkali metal sulfide for this purpose is sodium sulfide.

With respect to proportions, the concentration of the alkali metal or ammonium hydroxide or alkali metal or ammonium sulfide or polysulfide which is used in the reaction should be about 1.5 times on a molar basis, the concentration of the pyridinium salt. Optimum results are obtained by employing this reactant in a molar excess of about 50 percent. Moreover, it is preferable to employ a solvent or diluent in preparing these novel derivatives. Suitable solvents include water, lower alkanols such as methanol, ethanol, propanol, butanol and the like, dimethylsulfoxide, dioxane, dimethyl formamide, tetrahydrofuran and any other polar solvents which are inert under the conditions of the reaction.

The l-benzyl-3-carboxy-pyridinium chloride employed as the intermediate in the above described reactions, is itself prepared by reacting an aryl methylene chloride with nicotinic acid or with a ring substituted derivative thereof. This reaction is conveniently conducted at temperatures of from about l5 to about 150 C. although temperatures in the range of 25 to C. are preferred because of the ease of operating at these temperatures. This reaction can be conducted at atmospheric or superatmospheric pressure. While it is generally preferred to conduct this reaction at atmospheric pressure, autogeneous pressures developed while operating in a closed system are equally desirable. Stoichiometric amounts of the reactants can be employed in this reaction although it is preferred to employ a molar excess of the aryl methylene chloride. It is most preferred to employ a molar excess of this reactant of from about 20 to percent. Solvents or diluents can be effectively employed in conducting this reaction although they are not necessary. Exemplary of suitable solvents and diluents are water, lower alkanols such as methanol, ethanol, propanol, butanol and the like, dimethylsulfoxide, dioxane, dimethyl formamide, tetrahydrofuran or any other polar solvent which is inert to the reactants employed under the conditions of the reaction.

Although the processes used for the preparation of the complex mixtures of.compounds suitable for use in the plating process of this invention have been described with respect to the use, therein, of l-benzyl-3- carboxypyridinium chloride, it is also possible to employ other corresponding halide salts including the bromide and iodide salts. In addition, the benzyl and/or the pyridine rings of the pyridinium salt may be substituted with one or more non-interfering substituent, groups, i.e., with groups which will not interfere in-the reaction between the salt and the alkali metal or ammonium hydroxide, or the alkali metal or ammonium sulfide or polysulfide. Such non-interfering substituent groups include alkyl, aryl, arylalkyl, alkylaryl, alkoxy, aryloxy, halo and carbalkoxy groups.

With respect to the use of the above described complex mixtures as plating bath additives in the process of this invention, certain criteria should be noted. Thus, as has previously been stated, it is essential for such usage that these compounds be soluble in the plating solution or bath. More particularly, for use as plating bath additives, these complex mixtures of compounds should be soluble in water, at 20 C., in a concentration of at least about 0.] grams/liter.

Other requirements relating to the use of these complex mixtures as plating bath-additives include the fact that Z, in the above given formula. should not be a mercapto group and that R,, R, and R should,preferably, be devoid of any sulfur or sulfur containing substituents such as thioether, alkylthio, alkylthioalkyl, arylthio, alkylthioaryl, arylthioalkyl and polyalkylenethioglycol residues. Moreover, it should be noted that it is preferred, for plating bath usage, that M in the above formula should be a cation selected from the group consisting of H, Na*, K", NH, and the various above described alkyl ammonium cations. In addition, it is preferred that Y should be oxygen, i.e., -O-, or, that when Y is (8),, then x in the latter formula should have a value of 1 since enhanced results are obtained with either the ether or the monosulfide compounds. I

As previously noted, the use of the above described complex mixtures as brightening agents for cyanide zinc plating baths does not require their separation and isolation from the solutions in which they have been prepared. Thus, it is merely necessary to adjust the pH of this solution to a level of from about 6 to 10, and preferably about 7.5, by the addition of a suitable acid such, for example, as hydrochloric. Thereafter, the solution may be added to the plating bath formulation in an overall concentration such that the resulting plating bath contains from about 0.01 to 3.0 grams, on a dry solids basis, of the complex mixture of compounds per liter of plating bath solution. Optimum results appear to be obtained by the use of a concentration of about 0.1 grams of the complex mixture per liter of plating bath solution.

The plating bath solution, as is well known to those skilled in the art, will contain zinc ions derived from the usual sources which include metallic zinc or an oxide, hydroxide or cyanide salt of zinc. The bath will also ordinarily contain an alkali metal hydroxide, preferably sodium hydroxide, and an alkali metal cyanide salt, preferably sodium cyanide. Optimum results are obtained with a plating bath containing from about 30 to 37.5 grams per liter of zinc, from about 82 to 101 grams per literof sodium cyanide and fromabout 75 to 95 grams per liter of sodium hydroxide.

The novel brightening additives used in the process or this invention should preferably be used in conjunction with one more ofthe various materials heretofore used as brightening additives in cyanide zinc plating baths. Such brightening agents include soluble polymeric materials such, for example, as polyvinyl alcohol, gelatin, glue, gum tragacanth, gum arabic, gum ghatti, gum guaiac and agar-agar, the reaction product of hexamethylenetetramine and epichlorohydrin as described in US. Pat. No 3,227,638, protein based materials such as alph'a protein and meat protein hydrolysate, metallic brighteners such as water soluble nickel or molybdenum salts as well as aldehydes such as anisic, salicylic, vanillin, heliotropine, glutaraldehyde and the like. Preferred for this purpose is polyvinyl alcohol. Thus, it is to be noted that a preferred embodiment of the process of this invention involves the use, in a cyanide zinc plating bath, of one of the above described complex mixtures of pyridinium derivatives in combination with polyvinyl alcohol.

Various ferrous metals such, for example, as steel, may be zinc coated using plating baths containing one or both of the novel derivatives of this invention as brightening agents therein. In conducting the actual electroplating operation, current densities of from about 5 to 40, and preferably about 10-25, amperes per square feet (ASF) may be utilized.

The following examples will further illustrate the embodiment of this invention. In these examples, all parts given are by weight unless otherwise noted.

- EXAMPLE I This example illustrates the preparation, of a composition containing the sodium salt of di( l-benzyl-3- carboxyl-l,2-dihydropyridyl-2) ether, i.e.,

and which may also contain the corresponding isomers where the oxide group is attached to the 'dihydropyridine ring at the 4 position, i.e., a 1,4-dihydropyridyl-4 ether, and the six position, i.e., a 1,6-dihydropyridyl-6 ether.

Into a 1 liter, 3-neck flask equipped with a dropping funnel, stirrer and thermometer, there is added 20' the solution changes from color less to orange-red indicating the completion of the reaction. This solution contains 15.6 percent, by weight, of the desired ether derivatives.

A small portion of the solid reaction product is then isolated by distillation of the aqueous layer followed by extraction with methanol and subjected to infra-red, nuclear magnetic resonance and elemental analysis confirming the above given structure for this compound is at least one of its components.

Nitrogen Calc 5.7

Nitrogen Found 5.3

EXAMPLE II This example illustrates the preparation of a complex mixture containing sodium salts of di( l-benzyl-3- carboxyl-l ,2-dihydropyridyl-2) sulfide, i.e.,

and its 4 and 6 positional isomeric sulfides, the pyridinium sulfides, i.e.,

as well as other compounds such as the dipyridine compounds formed from the linking of two pyridine rings at the 2,4 and/or 6 positions on the respective rings.

To a 1 liter reaction flask at room temperature, there is added 25 grams (0.2 mole) of nicotinic acid, grams (0.4 mole) of benzyl chloride and 500 milliliters of methanol. The mixture is heated for hours at reflux.

After the heating period, the reaction mixture is distilled to approximately one quarter of its original volume and filtered. The filtrate is stripped to dryness to recover 26 grams (52 percent yield) of l-benzyl-3- carboxy-pyridinium chloride. The pyridinium chloride is then dissolved in 400 cc of water. The reaction mixture is heated to 45 C. and 6.2 grams (0.08 mole) of sodium sulfide dissolved in 114 cc of water is added over a 30 minute period. The mixture is then heated between 60-70 C. for 2 hours and stripped to dryness on.

a flash evaporator. A red-orange solid remains. Only the methanol soluble fraction is isolated as the product in a yield of 10 grams.

ANALYSIS Thin layer chromatography, liquid chromatography, mass spectral analysis, nuclear magnetic resonance and infra-red spectra indicate a complex mixture of compounds containing the structures described above.

EXAMPLE III 'This example illustrates the preparation of a complex mixture containing the potassium salts of the mixture of compounds whose preparation is described in Example II.

Thus, in preparing this product an equivalent amount 2 of potassium disulfide is substituted for the sodium sulfide reactant originally utilized in the procedure of Example II.

EXAMPLE IV.

This example illustrates the preparation of a complex mixture containing theammonium salts of the mixture of compounds whose preparation is described in Example II. q

Thus, in preparing this product a molar equivalent of ammonium tetrasulfide, i.e., [(NH ),S is substituted for the sodium sulfide originally used in the procedure of Example ll.

EXAMPLE V This example illustrates the preparation of a complex mixture of the barium, cadmium and zinc salts of the mixture of compounds whose preparation is described in'Example I]. I

Four one gram samples of the product of Example II are dissolved in 16 cc of methanol. Four aqueous solutions are then separately prepared as follows:

Salt Amount Water BaCl, 1 gram 20 cc. CdCl, 1 gram 20 cc. ZnCl, l gram 20 cc. BaCL/CdCl, 0.5/0.5 gram 20 cc.

Each one of the four aqueous salt solutions is added to a sample of the methanol solution of theproduct of Example Il. The corresponding barium, cadmium, zinc, and barium-cadmium (mixed) salts precipitate from their respective solutions and are recovered by filtration.

EXAMPLE VI EXAMPLE vn Grams Liter Zinc (as metal) 36.2 Sodium Cyanide 98.8 Sodium Hydroxide 78.3 Composition Containing The Sodium Salt of Di( l -benzyl-3 -carboxyl-l ,Z-dihydro-pyridyl- 2) ether 1.169

Polyvinyl Alcohol v 0.195

A two ampere Hull cell panel plated from this bath is lustrous, bright and smooth surfaced in the range of from 8 to 80 ASF and cloudy bright in the range of from l to 8 ASP. In contrast when this same plating is conducted using an identical plating bath which does not, however, contain the novel additive of this invention, the resulting zinc coating is non-lustrous, white in appearance andlacking in smoothness.

1 EXAMPLE VIII I This example illustrates theuse of the complex mixture containing sodium salts of di( l-benzyl-3-carboxyl- 1,2-dihydropyridyl-2) sulfide as a brightening agent-in an alkaline cyanide zincplating bath. A

The pH of the solution containing the sodium salts of di( 1 -benzyl-3-carboxyl-1 ,2-dihydropyridyl-2) sulfide whose preparation is described in Example 11, hereinabove, is adjusted to a value of 8 by the addition of hydrochloric acid. Thereafter, a portion of this solution is used in preparing an aqueous plating bath having the following composition: v

Grams Liter Mixture Containing The Sodium Saltof di( 1 -benzyl-3-carb oxyl-1 ,Z-di-hydropyridyl- 2 sulfide 0.75 Polyvinyl Alcohol 0.195 Zinc (as metal) 36 NaOH 76 99 A two ampere Hull cell panel is plated from this bath for 5 minutes using rod agitation. The deposit is hazy in the 0-9 ASF range, bright in the range of 9-75 ASP and cloudy bright in the range of 75-120 ASF.

EXAMPLE IX To the bath of Example VIII, there is added, in this instance, a total of 1.5 rather than of 0.75 gll of the mixture containing sulfide salt. A similar Hull Cell has EXAMPLE X ml/l of the reaction product of hexamethylenetetramine with epichlorohydrin whose preparation is described in U.S. Pat. No. 3,227,638. The zinc deposit from a 2 amp. Hull Cell plated for 5 minutes using rod agitation has the following characteristics:

0.8 ASF oailt dull 8-12 ASF Hazy 12-25 ASF Hazy Bright 25-120 ASF Very Bright EXAMPLE XI To a standard cyanide zinc electrolyte containing:

Grams Liter Zinc (as metal) 36 NaOH 76 NaCN 99 there is added 0.5 g/l of the mixture containing the sediumsalt of dihydropyridyl-2) ether.

A 2 ampere Hull cell panel is plated from this solution for 5 minutes with rod agitation. The deposit is cloudy between 0-6 ASF, very bright in the range of 6-20 ASP and cloudy bright-in the range of 20-100 ASF.

di( l-benzyl-3-carboxyl-l ,2-

7 EXAMPLE Xll EXAMPLE Xlll in this case, a total of 1.0 g/l of the mixture containing the ether which is used in Examples X1 and X1! is presentin the plating bath. AHull Cellpanel is plated under similar conditions from this bath. The deposit is cloudy bright in the range of 0-8 ASP and bright in the range of 8-100 ASF.

EXAMPLE XIV This example illustrates the use of various grades of polyvinyl alcohol in plating baths containing one of the novel additives of this invention.

To a number of samples of the plating bath having the composition set forth below, there is added, respectively, the different grades of polyvinyl alcohol described in Table 1. This table also describes the results p v To the bath of Example IX, there is also added 0.94

obtained in each case as well as the concentration of the polyvinyl alcohol.

Zinc (as metal) 1 36 g/l NaOH 1 76 g/l NaCN 99 gll Mixture containing the lodlum salt of di(l-benzyl-S-carboxyl-l,Z-dihydrcpyrldyl- 2)sulflde 0.94 gll The reaction roduct of hexa-metlly ene-tetrarnine and eip-chlorohydrin described in U.S. Pat. No. 3,227,638 0.94 rnl/l TABLE I Hydrol- Concen- Viscosysis, tration, ity 3 in mole Polyvinyl alcohol added g./l. cps. percent Appearance of deposit lClvunol 1 51-05 0.195 4-6 88. 2-89. 2 -1 ASF dull.

. 1-15 ASF pitted.

15-120 ASF bright.

Elvnnol 50-42 0. 05 35-45 87-89 0-8 ASE dull.

8-80 ASF bright. 80-120 ASF very slight haze.

Elvanol 70-05 0. 05 4-6 99-100 0-10 ASF dull.

10-38 ASF bright. 38-120 ASF hazy.

Elvanol 1 52-22 0.1 21-25 87-89 0-10 ASF dull.

10-60 ASF bright. 60-120 ASF hazy.

Gelvatol 40-10 0.15 1. 3-2 72. 9-77 0-7 ASF dull.

7-55 ASF bright. 55-120 ASF hazy.

Gelvatol 2 40-20 0. 2-3 72. 9-77 0-7 ASF dull.

7-18 ASF hazy. 18-60 ASF bright. 60-120 ASF very slight haze.

Gelvatol 2 1-30 0. 1 4-6 98. 5-100 0-6 ASF dull.

6-18 ASF hazy. 18-120 ASF bright.

Gelvatol 1 20-30 0.15 4-6 72. 9-77 0-8 ASF dull.

8-20 ASF slight haze. 20-65 ASF bright. 66-120 ASF very slight haze.

l Trademark-of the E. I. du Pont & de Nernours & Co. 2 Trademark of Shawinigan Products Corp.

3 Determined by the Hoeppler falling ball procedure using a 4%, by weight, aqueous solution at 20 C.

EXAMPLE XV This example illustrates the use of gelatine in a plating bath containing one of the additives of this invention.

A plating bath having the following formulation is prepared:

Zinc (as metal) 36 g/l NaOH 76 'g/l NaCN 99 g/l Mixture containing sodium salt of di( 1-benzyl-3-carboxyl-1,2-dihydropyridyl- 2) sulfide 0.94 g/l The reaction product of hexamethylene-tetmnine and eipchlorohydrin described in U.S. Pat. No.

3,227,638 0.94 mil! Gelatine (50 bloom) 0.15 g/l The zinc deposit from a 2 amp. Hull Cell plated for 5 minutes using rod agitation has the following characteristics:

0-6 ASF Dull 6-12 Bright 12-20 ASF Hazy 20-50 ASF Bright 50-120 ASF Very slight haze EXAMPLE XV I This example illustrates the use of nickel sulfate in a plating bath containing one of the novel additives of this invention:

A plating bath having the following formulation is prepared:

Zinc'(as metal) 36 g/l NaOH 76 g/l NaCN 99 g/l Mixture containing sodium salt of di( l-benzyl-3-carboxyll ,Z-dihydropyridyl- 2) sulfide 0.94 g/l The reaction roduct of hexa-methy ene-tetmmine and eip-chlorohydrin described in U.S. Pat. No.

3,227,638 0.94 mgll Nickel sulfate 0.1376 gll This zinc deposit from a 2 amp. Hull Cell plated for 5 minutes using rod agitation has the following characteristics:

O-l ASF Dull 1-6 ASF Skip plate 6-12 ASF Very slight haze 12-40 ASF Bright 40-120 ASF Very slight haze Variations in proportion, procedures and materials may be made without departing from the scope of this invention as defined in the following claims.

What is claimed is:

1. In an aqueous alkaline cyanide zinc bath for the electrodeposition of zinc, the improvement which comprises having dissolved in said bath a complex mixture of compounds which include those corresponding to the formulae:

, UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION P t t N D t d August 28,

Invmnmr s Richard P. Cope, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 17, delete "hexoxy", second occurrence.

Column 13, Claim 4, second line, "salf" should read salt Signed and Scaled this Sixth Day of September 1977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Attesting Officer Acting Commissioner of Patents and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 5,755,097 Page 1 of 2 DATED August 28, 973

|NVENTOR(S) Richard P. Cope, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

CH2 Y" and/or 2YH Col. 6, line 56, after the word "and" insert the word --at--.

Col. 6, line 2, delete the word "or" and in its place insert the word --of- Col. 7, Example II, second formula, the bottom benzene ring has an H coming from the right hand corner,- this should be deleted and the formula should read as follows:

(Continued -on next page) UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1,755,097 DATED Au ust 28, 1975 age 2 of z INV ENTOR(S) I Richard P. Cope, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE CLAIMS Claims 2, 5, i, 5, 6 and 7 should read "Claim 1" instead of "Claim 81' Claims 9, 1o, 11, 12, 15 and 14 should read "Claim 8" instead of"Claim l5".

Signed and Scaled this twelfth Day Of July 1977 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting oflicer Commissioner of Patents and Trademarks 

2. The bath of claim 8, wherein Y in said compounds is oxygen.
 3. The bath of claim 8, wherein Y in said compounds is (S)x.
 4. The bath of claim 8, wherein said complex mixture of compounds contains the sodium salf of di(1-benzyl-3-carboxyl-1,2-dihydropyridyl-2) ether.
 5. The bath of claim 8, wherein said complex mixture of compounds contains the sodium salt of di(1-benzyl-3-carboxyl-1,2-dihydropyridyl-2) sulfide.
 6. The bath of claim 8, wherein polyvinyl alcohol is also present.
 7. The bath of claim 8, wherein gelatine is also present.
 8. In the process of electrodepositing zinc from an aqueous alkaline cyanide zinc bath, the improvement which comprises the dissolution in said bath of a complex mixture of compounds which include those corresponding to the formulae:
 9. The process of claim 15, wherein Y in said compounds is oxygen.
 10. The process of claim 15, wherein Y in said compounds is (S)x.
 11. The process of claim 15, wherein said complex mixture of compounds contains the sodium salt of di(1-benzyl-3-carboxyl-1,2-dihydropyridyl-2) ether.
 12. The process of claim 15, wherein said complex mixture of compounds contains the sodium salt of di(1-benzyl-3-carboxyl-1,2-dihydropyridyl-2) sulfide.
 13. The process of claim 15, wherein polyvinyl alcohol is also present in said bath.
 14. The process of claim 15, wherein gelatine is also present in said bath. 